Uniting of fusible porcelain to a precious metal base member

ABSTRACT

FUSIBLE PORCELAIN IS UNITED IN A THIN LAYER TO A PRECIOUS METAL BASE MEMBER BY FIRST FORMING ON SUCH PRECIOUS METAL BASE MEMBER A GOLD COAT HAVING A CARPET-LIKE, IRREGULAR SURFACE COMPOSED OF GOLD PARTICLES WHICH ARE SOLDERED OR SWEATED TO THE BASE MEMBER AND ARE LATERALLY SEPARATED FROM EACH OTHER, AND THEN APPLYING TO SUCH CARPET-LIKE, IRREGULAR SURFACE A PASTE OF A RELATIVELY LOWFUSING PORCELAIN WHICH UPON BEING FUSED IN SITU IS MECHANICALLY UNITED TO SAID CARPET-LIKE SURFACE BY INTERLOCKING TO SUCH GOLD PARTICLES. THE INTERLOCK THUS FORMED OF THE PORCELAIN LAYER WITH THE PURE GOLD PARTICLES HAS BEEN FOUND TO PERMIT OF LIMITED DIFFERENTIAL EXPANSION AND CONTRACTION BETWEEN THE PORCELAIN LAYER AND THE BASE MEMBER UNDER THE SAME HEAT CONDITIONS DUE TO THE FACT THAT THE PURE GOLD PARTICLES YIELD WITH MOVEMENT OF THE PORCELAIN. THERE IS ALSO PROVIDED TH NOVEL COMPOSITE STRUCTURE OF A PRECIOUS METAL BASE MEMBER, A GOLD COAT LAYER HAVING SPACED GOLD PARTICLES SOLDERED OR SWEATED T THE BASE MEMBER, AND A PORCELAIN LAYER INTERLOCKED TO SUCH GOLD COAT PARTICLES.

E. M. PRosEN June 15, 1971 UNITING OF FUSIBLE PORCELAIN TO A PRECIOUSMETAL BASE MEMBER Filed May 3l, 1958 s luslllll INVENTOR. 7m /V /DRSf/VUnited States Patent O 3,585,064 UNITING OF FUSIBLE PORCELAIN TO APRECIOUS METAL BASE MEMBER Emil M. Prosen, Bala-Cynwyd, Pa., assignor toNobllium Products, Inc., Philadelphia, Pa. Filed May 31, 1968, Ser. No.733,387 Int. Cl. B44d 1/14 U.S. Cl. 117-70C 5 Claims ABSTRACT OF THEDISCLOSURE Fusible porcelain is united in a thin layer to a preciousmetal base member by iirst forming on such preclous, metal base member agold coat having a carpet-like, irregular surface composed of goldparticles which are soldered or sweated to the base member and arelaterally separated from each other, and then applying to suchcarpet-like, irregular surface a paste of a relatively lowfusingporcelain which upon being fused in situ is mechanically united to saidcarpet-like surface by interlocking to such gold particles. Theinterlock thus formed of the porcelain layer with the pure goldparticles has been found to permit of limited differential expansion andcontraction between the porcelain layer and the base member under thesame heat conditions due to the fact that the pure gold particles yield'with movement of the porcelain. There is also provided the novelcomposite structure of a precious metal base member, a gold coat layerhaving spaced gold particles soldered or sweated to the base member, anda porcelain layer interlocked to such gold coat particles.

The present invention relates to the uniting of fusible porcelain to aprecious metal base member, and aims to provide certain improvementstherein.

It is well known in the art that porcelain cannot be bonded by fusion tothe surface of a precious metal base member, such as pure gold orplatinum, for the reason that they do not form an oxide. Accordingly, inthe art, and especially in the dental profession, when it was desired tobond porcelain to pure gold it was the usual practice to add iron orsome other readily oxidizable metal to the gold to promote adhesionthereto of the porcelain. Such procedure, however, has not been entirelysatisfactory 'because the expansion and contraction of gold andporcelain under the same heat conditions differ greatly and give rise tostrains being set up in the porcelain, which strains become evident bycrazing of the porcelain especially where present in a thin layer.Moreover, the bond between the oxide present in the gold and theporcelain is not as strong as desirable and the presence of the addedoxide imparts, by reflected light, an unwanted coloration to theporcelain.

It is an object of the present invention to overcome the foregoingshortcomings of the prior art relating to the fusion of porcelain to aprecious metal base member, especially pure gold, and to provide thecomposite structure of a precious metal base member, a gold particlelayer soldered or sweated to the surface of such base member, and afused porcelain layer rmly interlocked to such gold particle layer.

A further object of the invention is to provide a method of unitingfusible porcelain to a gold base member whereby the interlocking betweensuch porcelain and base member is so strong as to render it practicallyimpossible to physically separate the porcelain from the gold afterbeing united thereon.

The foregoing and other objects of the invention, not specificallyenumerated, will become evident and better understood from the detaileddescription which follows Iwhen considered in connection with theaccompanying drawing wherein:

FIG. 1 is a front elevation of an incisor tooth crown embodying theinvention;

FIG. 2 is a longitudinal section taken along the line 2 2 of the toothcrown shown in FIG. 1;

FIG. 3 is a transverse section taken along the line 3 3 of FIG. 2;

FIG. 4 is a photo-micrograph of the surface of a gold coat formed inaccordance with the invention, the photomicrograph being made from ailat surface in order to get the proper focal depth to show thecarpet-like, irregular surface appearance;

FIG. 5 is a photo-micrograph taken along the line 5-5 of FIG. 3.

Referring to the drawing, the invention is illustrated as applied to aporcelain facing on an incisor tooth crown 10, which consists of a castprecious metal cap 12, such as pure gold, upon the outer surface ofwhich is formed a composite gold coat 14 consisting of a first golddeposit 14a and a second gold deposit 14b. Over the outer surface of thedeposit 14b is formed a porcelain overlay 16 which is fused in situ andinterlocked to the second gold deposit to provide a tooth-like bodyhaving the desired contour in relation to the companion teeth in apersons mouth.

The gold cap 12 is formed as a casting in accordance with well-knowndental techniques.

The composite gold coat 14 is formed in two steps in the followingmanner: A viscous slurry or paste is first formed by mixing in properproportion powdered pure gold of approximately 325 mesh, powdered silverof 400 mesh or finer, a lluxing composition and a suitable wettingagent. A combined fluxing and wetting agent which I have found suitableconsists of the following constituents in approximately the followingproportions: 12 grains sodium Illuoride, 6 grains borax and 2pennyweights ethylene glycol containing 6 grains of titanium oxide. Themixture is whipped in a blender to a creamy consistency and 2pennyweights of the cream is added to 4 pennyweights of the powderedgold and 10 grains of the powdered silver, e.g., about 10% of silver inrelation to the gold, and are thoroughly stirred to make a suitablepaste. If found necessary this paste may be diluted with a drop or twoof water or glycerine to render its consistency suitable. It

is then painted on the area of the precious metal surface to 'which aporcelain facing is to be united (herein shown as the outer surface ofthe pure gold tooth crown 12), then dried, the coated crown placed in afurnace, and the temperature of the furnace progressively elevated to1945 F., the melting point of pure gold. In the presence of silver andthe flux, the particles of gold may be induced to melt at approximately1940 F. When the gold in the applied paste melts, it flashes andproduces a gold alloy deposit which will be of lower carat gold andhence will have a lower melting point than pure gold. The flashedsurface constitutes the first gold deposit 14a. The major portion of thefluxing agent Iwill ilow off from the flashed gold-silver alloy and anyflux that remains may prove useful when fusing thereon the second golddeposit 14b.

To form the gold deposit 14h a second application of the aforementionedslurry or paste is painted on the surface of the cooled first deposit14a to provide thereon a layer containing gold particles which areseparated from one another by the titanium oxide contained incombination with the flux. The second applied paste layer is thenthoroughly dried, the crown placed in the furnace and the temperaturethereof progressively elevated. Here again as in the preparation of therst deposit 14a the 10% silver in the paste starts to melt at about1769" F. and gravitates into contact with the alloy deposit 14a, whilethe gold particles are -held in Mil/l l y the oxide 1n e Hux. As theMnperature 1n the fu approaches 1915 F. and all the sil er will have bee molten and the major por tion of the flux and the titanium Xide willhave become molten and owed o from the article, the temperature iselowered i lnediately or the article is emo d from the furnace. The goldparticles are no per itted 1219]( hence upon cooling, the gold particlesbeg() or sw ated to the rst deposit (I mediary of he neW olten t pasteentering into the spaces in the irregular surand wetting agent consistsof ethylene glycol, titanium face and covering said surface, anddioxide, sodium fluoride and borax. (h) fusing the porcelain paste insitu to cause an interlocking of the porcelain with the gold coat,References Cited whereby expansion and contraction of the porcelain 5UNITED STATES PATENTS layer can take place lndependently of theexpansion I 191 1/ 62 C and contraction of the gold coat upon which itis 3018 19 aba 117"70(A) rlltliterclis when subjected to the sametemperature con- ALFRED L. LEAVITT Primary Examiner `4. A methodaccording to claim 3 wherein the powdered 10 C. K. WEIFFENBACH,Assistant Examiner pure gold and powdered silver in the slurry is in theproportion of `4 pennyweights of gold to 10 grains of U-SC1 X-R- Silver-117-70A, 71M, 94

5. A method according to clarm 3 wherein the ilux UNITED STATES MTENT@PRICE CERTIFCATE 0F CGRRECTION Patent No. 'ggg-L06); Dated June lL lq'lInventor@ EMIL M. PROSEN It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

Abstract of' the Disclosure Signed and sealed this 25th dey of April1972.

(SEAL) Attest:

EDWARD M.FLETCID:JR,JH. Attestng Officer ROBERT GOTTSCHALK Commissionerof Patents FORM Po-1050,(\o69) i U S. GOVERNMENT ?R NTING OFFICE |969O-Ji-l

